Case 78. Cryptococcal granuloma of lung (49 y-o M)
Solitary subpleural lung nodule excised thoracoscopically
Key words : Cryptococcus neoformans, cryptococcal granuloma
An irregular-shaped yellowish nodule is seen (gross findings).   Multinucleated giant cells contain numbers of haloed, unstained yeasts, Cryptococcus neoformans (HE). Fibroblastic activation is associated with the granulomatous reaction.
PAS stain identifies numerous yeast-form fungi phagocytized by multinucleated giant cells.   Electron micrograph demonstrates encapsulated round yeasts in the cytoplasm. A nucleus is recognized in the yeast.
Reference case 78A
Brushing cytology showing a multinucleated giant cell which phagocytizes round yeasts into the cytoplasm (Papanicolaou). Cryptococcus neoformans proliferate within the cell, and the main defense mechanism against this yeast is the cellular immunity.
  Reference case 78A
Brushing cytology showing a multinucleated giant cell which phagocytizes numbers of PAS-positive round yeasts into the cytoplasm (PAS). When phagocytized, the size of this yeast becomes smaller, and capsule formation becomes inactive.
Reference case 78B
Caseating granuloma formed at the periphery of the lung (HE). The low power view is indistinguishable from tuberculosis in this case. PAS and Grocott stains identify the yeast in epithelioid cells and among the necrotic material.
  Reference case 78C
Opportunistic infection in an immunosuppressed patient, without provoking granulomatous host reaction (HE). Large-sized yeast form fungi are floating in the mucoid matrix. Thick capsules are formed, when they are located outside the phagocytes.
Reference case 78C
Argentaffin reaction seen in the cell wall of Cryptococcus neoformans (Fontana-Masson). It is of note that C. neoformans is stained with Fontana-Masson's argentaffin reaction. The other brown fungi are also positive. The size of the yeasts becomes much larger, when they grow outside the cell.